Wireless communications systems have become a widespread approach to communicating speech and data. Many types of devices, such as pagers and cellular phones, use wireless communications to increase their mobility. Various standards or protocols have been developed to provide a wide variety of services and to satisfy the needs of consumers. One such standard, known as the Digital European Cordless Telecommunications (DECT) standard, provides access to a variety of networks, e.g., Global System for Mobile Communications (GSM), Integrated Services Digital Network (ISDN), and Public Switched Telephone Network (PSTN) through standards known as DECT profiles.
Users within a DECT system share a band on the frequency spectrum. With the users sharing a frequency band, DECT systems transmit speech and data using approaches collectively known as time division multiple access (TDMA). In TDMA, communication time is divided into time intervals known as frames. The DECT standard, for example, defines frames as 10 millisecond intervals. Each frame is further divided into divisions known as slots. Speech and data from each user are stored and compressed as data packets. The system transmits data packets during selected slots. Each device in a DECT system is assigned one or more slots identifying the device as the source of data packets transmitted during the assigned slots.
Many TDMA systems are susceptible to delays that potentially result in lost data or incorrect identification of sources of data packets. Such delays are attributable to, for example, the distance between a handset or mobile station and its corresponding base station. These delays typically vary between individual devices within a cell, rendering synchronization of the devices difficult.
Some TDMA approaches switch data packets at fixed time intervals after receiving the beginning of a data packet in order to compensate for communication delays. The fixed interval includes some allowance for delays. In certain applications, the delays can exceed this allowance. When the delay exceeds the allowance, data packets may be truncated prematurely, resulting in lost data.
Certain other TMDA techniques use software to measure the amount of delay in receiving data from the base station. Such software techniques compensate for delays by commanding the radio controller to deactivate the radio at a later time, e.g., one or two bits later. With software compensating for the delays, the software becomes more complex. Moreover, power consumption increases, reducing battery lifetimes.